Explanation:

- Laterite Soil: Formed in tropical regions with heavy rainfall, laterite soil is rich in iron oxides. The red color is due to leaching and oxidation of iron.

- Red Soil: Named for its red color, which is due to the diffusion of iron oxides. It forms in a hot, dry climate with good drainage.

- Regur Soil: Also known as black cotton soil, it’s high in clay and lacks the red hue due to iron presence.

- Alluvial Soil: Carried by rivers, it's typically more fertile and not red from iron.